1# SPDX-License-Identifier: GPL-2.0 2# 3# General architecture dependent options 4# 5 6# 7# Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can 8# override the default values in this file. 9# 10source "arch/$(SRCARCH)/Kconfig" 11 12menu "General architecture-dependent options" 13 14config CRASH_CORE 15 bool 16 17config KEXEC_CORE 18 select CRASH_CORE 19 bool 20 21config KEXEC_ELF 22 bool 23 24config HAVE_IMA_KEXEC 25 bool 26 27config HOTPLUG_SMT 28 bool 29 30config OPROFILE 31 tristate "OProfile system profiling" 32 depends on PROFILING 33 depends on HAVE_OPROFILE 34 select RING_BUFFER 35 select RING_BUFFER_ALLOW_SWAP 36 help 37 OProfile is a profiling system capable of profiling the 38 whole system, include the kernel, kernel modules, libraries, 39 and applications. 40 41 If unsure, say N. 42 43config OPROFILE_EVENT_MULTIPLEX 44 bool "OProfile multiplexing support (EXPERIMENTAL)" 45 default n 46 depends on OPROFILE && X86 47 help 48 The number of hardware counters is limited. The multiplexing 49 feature enables OProfile to gather more events than counters 50 are provided by the hardware. This is realized by switching 51 between events at a user specified time interval. 52 53 If unsure, say N. 54 55config HAVE_OPROFILE 56 bool 57 58config OPROFILE_NMI_TIMER 59 def_bool y 60 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64 61 62config KPROBES 63 bool "Kprobes" 64 depends on MODULES 65 depends on HAVE_KPROBES 66 select KALLSYMS 67 help 68 Kprobes allows you to trap at almost any kernel address and 69 execute a callback function. register_kprobe() establishes 70 a probepoint and specifies the callback. Kprobes is useful 71 for kernel debugging, non-intrusive instrumentation and testing. 72 If in doubt, say "N". 73 74config JUMP_LABEL 75 bool "Optimize very unlikely/likely branches" 76 depends on HAVE_ARCH_JUMP_LABEL 77 depends on CC_HAS_ASM_GOTO 78 help 79 This option enables a transparent branch optimization that 80 makes certain almost-always-true or almost-always-false branch 81 conditions even cheaper to execute within the kernel. 82 83 Certain performance-sensitive kernel code, such as trace points, 84 scheduler functionality, networking code and KVM have such 85 branches and include support for this optimization technique. 86 87 If it is detected that the compiler has support for "asm goto", 88 the kernel will compile such branches with just a nop 89 instruction. When the condition flag is toggled to true, the 90 nop will be converted to a jump instruction to execute the 91 conditional block of instructions. 92 93 This technique lowers overhead and stress on the branch prediction 94 of the processor and generally makes the kernel faster. The update 95 of the condition is slower, but those are always very rare. 96 97 ( On 32-bit x86, the necessary options added to the compiler 98 flags may increase the size of the kernel slightly. ) 99 100config STATIC_KEYS_SELFTEST 101 bool "Static key selftest" 102 depends on JUMP_LABEL 103 help 104 Boot time self-test of the branch patching code. 105 106config OPTPROBES 107 def_bool y 108 depends on KPROBES && HAVE_OPTPROBES 109 select TASKS_RCU if PREEMPTION 110 111config KPROBES_ON_FTRACE 112 def_bool y 113 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 114 depends on DYNAMIC_FTRACE_WITH_REGS 115 help 116 If function tracer is enabled and the arch supports full 117 passing of pt_regs to function tracing, then kprobes can 118 optimize on top of function tracing. 119 120config UPROBES 121 def_bool n 122 depends on ARCH_SUPPORTS_UPROBES 123 help 124 Uprobes is the user-space counterpart to kprobes: they 125 enable instrumentation applications (such as 'perf probe') 126 to establish unintrusive probes in user-space binaries and 127 libraries, by executing handler functions when the probes 128 are hit by user-space applications. 129 130 ( These probes come in the form of single-byte breakpoints, 131 managed by the kernel and kept transparent to the probed 132 application. ) 133 134config HAVE_EFFICIENT_UNALIGNED_ACCESS 135 bool 136 help 137 Some architectures are unable to perform unaligned accesses 138 without the use of get_unaligned/put_unaligned. Others are 139 unable to perform such accesses efficiently (e.g. trap on 140 unaligned access and require fixing it up in the exception 141 handler.) 142 143 This symbol should be selected by an architecture if it can 144 perform unaligned accesses efficiently to allow different 145 code paths to be selected for these cases. Some network 146 drivers, for example, could opt to not fix up alignment 147 problems with received packets if doing so would not help 148 much. 149 150 See Documentation/unaligned-memory-access.txt for more 151 information on the topic of unaligned memory accesses. 152 153config ARCH_USE_BUILTIN_BSWAP 154 bool 155 help 156 Modern versions of GCC (since 4.4) have builtin functions 157 for handling byte-swapping. Using these, instead of the old 158 inline assembler that the architecture code provides in the 159 __arch_bswapXX() macros, allows the compiler to see what's 160 happening and offers more opportunity for optimisation. In 161 particular, the compiler will be able to combine the byteswap 162 with a nearby load or store and use load-and-swap or 163 store-and-swap instructions if the architecture has them. It 164 should almost *never* result in code which is worse than the 165 hand-coded assembler in <asm/swab.h>. But just in case it 166 does, the use of the builtins is optional. 167 168 Any architecture with load-and-swap or store-and-swap 169 instructions should set this. And it shouldn't hurt to set it 170 on architectures that don't have such instructions. 171 172config KRETPROBES 173 def_bool y 174 depends on KPROBES && HAVE_KRETPROBES 175 176config USER_RETURN_NOTIFIER 177 bool 178 depends on HAVE_USER_RETURN_NOTIFIER 179 help 180 Provide a kernel-internal notification when a cpu is about to 181 switch to user mode. 182 183config HAVE_IOREMAP_PROT 184 bool 185 186config HAVE_KPROBES 187 bool 188 189config HAVE_KRETPROBES 190 bool 191 192config HAVE_OPTPROBES 193 bool 194 195config HAVE_KPROBES_ON_FTRACE 196 bool 197 198config HAVE_FUNCTION_ERROR_INJECTION 199 bool 200 201config HAVE_NMI 202 bool 203 204# 205# An arch should select this if it provides all these things: 206# 207# task_pt_regs() in asm/processor.h or asm/ptrace.h 208# arch_has_single_step() if there is hardware single-step support 209# arch_has_block_step() if there is hardware block-step support 210# asm/syscall.h supplying asm-generic/syscall.h interface 211# linux/regset.h user_regset interfaces 212# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 213# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 214# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 215# signal delivery calls tracehook_signal_handler() 216# 217config HAVE_ARCH_TRACEHOOK 218 bool 219 220config HAVE_DMA_CONTIGUOUS 221 bool 222 223config GENERIC_SMP_IDLE_THREAD 224 bool 225 226config GENERIC_IDLE_POLL_SETUP 227 bool 228 229config ARCH_HAS_FORTIFY_SOURCE 230 bool 231 help 232 An architecture should select this when it can successfully 233 build and run with CONFIG_FORTIFY_SOURCE. 234 235# 236# Select if the arch provides a historic keepinit alias for the retain_initrd 237# command line option 238# 239config ARCH_HAS_KEEPINITRD 240 bool 241 242# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 243config ARCH_HAS_SET_MEMORY 244 bool 245 246# Select if arch has all set_direct_map_invalid/default() functions 247config ARCH_HAS_SET_DIRECT_MAP 248 bool 249 250# 251# Select if arch has an uncached kernel segment and provides the 252# uncached_kernel_address / cached_kernel_address symbols to use it 253# 254config ARCH_HAS_UNCACHED_SEGMENT 255 select ARCH_HAS_DMA_PREP_COHERENT 256 bool 257 258# Select if arch init_task must go in the __init_task_data section 259config ARCH_TASK_STRUCT_ON_STACK 260 bool 261 262# Select if arch has its private alloc_task_struct() function 263config ARCH_TASK_STRUCT_ALLOCATOR 264 bool 265 266config HAVE_ARCH_THREAD_STRUCT_WHITELIST 267 bool 268 depends on !ARCH_TASK_STRUCT_ALLOCATOR 269 help 270 An architecture should select this to provide hardened usercopy 271 knowledge about what region of the thread_struct should be 272 whitelisted for copying to userspace. Normally this is only the 273 FPU registers. Specifically, arch_thread_struct_whitelist() 274 should be implemented. Without this, the entire thread_struct 275 field in task_struct will be left whitelisted. 276 277# Select if arch has its private alloc_thread_stack() function 278config ARCH_THREAD_STACK_ALLOCATOR 279 bool 280 281# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 282config ARCH_WANTS_DYNAMIC_TASK_STRUCT 283 bool 284 285config ARCH_32BIT_OFF_T 286 bool 287 depends on !64BIT 288 help 289 All new 32-bit architectures should have 64-bit off_t type on 290 userspace side which corresponds to the loff_t kernel type. This 291 is the requirement for modern ABIs. Some existing architectures 292 still support 32-bit off_t. This option is enabled for all such 293 architectures explicitly. 294 295config HAVE_ASM_MODVERSIONS 296 bool 297 help 298 This symbol should be selected by an architecure if it provides 299 <asm/asm-prototypes.h> to support the module versioning for symbols 300 exported from assembly code. 301 302config HAVE_REGS_AND_STACK_ACCESS_API 303 bool 304 help 305 This symbol should be selected by an architecure if it supports 306 the API needed to access registers and stack entries from pt_regs, 307 declared in asm/ptrace.h 308 For example the kprobes-based event tracer needs this API. 309 310config HAVE_RSEQ 311 bool 312 depends on HAVE_REGS_AND_STACK_ACCESS_API 313 help 314 This symbol should be selected by an architecture if it 315 supports an implementation of restartable sequences. 316 317config HAVE_FUNCTION_ARG_ACCESS_API 318 bool 319 help 320 This symbol should be selected by an architecure if it supports 321 the API needed to access function arguments from pt_regs, 322 declared in asm/ptrace.h 323 324config HAVE_CLK 325 bool 326 help 327 The <linux/clk.h> calls support software clock gating and 328 thus are a key power management tool on many systems. 329 330config HAVE_HW_BREAKPOINT 331 bool 332 depends on PERF_EVENTS 333 334config HAVE_MIXED_BREAKPOINTS_REGS 335 bool 336 depends on HAVE_HW_BREAKPOINT 337 help 338 Depending on the arch implementation of hardware breakpoints, 339 some of them have separate registers for data and instruction 340 breakpoints addresses, others have mixed registers to store 341 them but define the access type in a control register. 342 Select this option if your arch implements breakpoints under the 343 latter fashion. 344 345config HAVE_USER_RETURN_NOTIFIER 346 bool 347 348config HAVE_PERF_EVENTS_NMI 349 bool 350 help 351 System hardware can generate an NMI using the perf event 352 subsystem. Also has support for calculating CPU cycle events 353 to determine how many clock cycles in a given period. 354 355config HAVE_HARDLOCKUP_DETECTOR_PERF 356 bool 357 depends on HAVE_PERF_EVENTS_NMI 358 help 359 The arch chooses to use the generic perf-NMI-based hardlockup 360 detector. Must define HAVE_PERF_EVENTS_NMI. 361 362config HAVE_NMI_WATCHDOG 363 depends on HAVE_NMI 364 bool 365 help 366 The arch provides a low level NMI watchdog. It provides 367 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 368 369config HAVE_HARDLOCKUP_DETECTOR_ARCH 370 bool 371 select HAVE_NMI_WATCHDOG 372 help 373 The arch chooses to provide its own hardlockup detector, which is 374 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 375 interfaces and parameters provided by hardlockup detector subsystem. 376 377config HAVE_PERF_REGS 378 bool 379 help 380 Support selective register dumps for perf events. This includes 381 bit-mapping of each registers and a unique architecture id. 382 383config HAVE_PERF_USER_STACK_DUMP 384 bool 385 help 386 Support user stack dumps for perf event samples. This needs 387 access to the user stack pointer which is not unified across 388 architectures. 389 390config HAVE_ARCH_JUMP_LABEL 391 bool 392 393config HAVE_ARCH_JUMP_LABEL_RELATIVE 394 bool 395 396config HAVE_RCU_TABLE_FREE 397 bool 398 399config HAVE_RCU_TABLE_NO_INVALIDATE 400 bool 401 402config HAVE_MMU_GATHER_PAGE_SIZE 403 bool 404 405config HAVE_MMU_GATHER_NO_GATHER 406 bool 407 408config ARCH_HAVE_NMI_SAFE_CMPXCHG 409 bool 410 411config HAVE_ALIGNED_STRUCT_PAGE 412 bool 413 help 414 This makes sure that struct pages are double word aligned and that 415 e.g. the SLUB allocator can perform double word atomic operations 416 on a struct page for better performance. However selecting this 417 might increase the size of a struct page by a word. 418 419config HAVE_CMPXCHG_LOCAL 420 bool 421 422config HAVE_CMPXCHG_DOUBLE 423 bool 424 425config ARCH_WEAK_RELEASE_ACQUIRE 426 bool 427 428config ARCH_WANT_IPC_PARSE_VERSION 429 bool 430 431config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 432 bool 433 434config ARCH_WANT_OLD_COMPAT_IPC 435 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 436 bool 437 438config HAVE_ARCH_SECCOMP_FILTER 439 bool 440 help 441 An arch should select this symbol if it provides all of these things: 442 - syscall_get_arch() 443 - syscall_get_arguments() 444 - syscall_rollback() 445 - syscall_set_return_value() 446 - SIGSYS siginfo_t support 447 - secure_computing is called from a ptrace_event()-safe context 448 - secure_computing return value is checked and a return value of -1 449 results in the system call being skipped immediately. 450 - seccomp syscall wired up 451 452config SECCOMP_FILTER 453 def_bool y 454 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 455 help 456 Enable tasks to build secure computing environments defined 457 in terms of Berkeley Packet Filter programs which implement 458 task-defined system call filtering polices. 459 460 See Documentation/userspace-api/seccomp_filter.rst for details. 461 462config HAVE_ARCH_STACKLEAK 463 bool 464 help 465 An architecture should select this if it has the code which 466 fills the used part of the kernel stack with the STACKLEAK_POISON 467 value before returning from system calls. 468 469config HAVE_STACKPROTECTOR 470 bool 471 help 472 An arch should select this symbol if: 473 - it has implemented a stack canary (e.g. __stack_chk_guard) 474 475config CC_HAS_STACKPROTECTOR_NONE 476 def_bool $(cc-option,-fno-stack-protector) 477 478config STACKPROTECTOR 479 bool "Stack Protector buffer overflow detection" 480 depends on HAVE_STACKPROTECTOR 481 depends on $(cc-option,-fstack-protector) 482 default y 483 help 484 This option turns on the "stack-protector" GCC feature. This 485 feature puts, at the beginning of functions, a canary value on 486 the stack just before the return address, and validates 487 the value just before actually returning. Stack based buffer 488 overflows (that need to overwrite this return address) now also 489 overwrite the canary, which gets detected and the attack is then 490 neutralized via a kernel panic. 491 492 Functions will have the stack-protector canary logic added if they 493 have an 8-byte or larger character array on the stack. 494 495 This feature requires gcc version 4.2 or above, or a distribution 496 gcc with the feature backported ("-fstack-protector"). 497 498 On an x86 "defconfig" build, this feature adds canary checks to 499 about 3% of all kernel functions, which increases kernel code size 500 by about 0.3%. 501 502config STACKPROTECTOR_STRONG 503 bool "Strong Stack Protector" 504 depends on STACKPROTECTOR 505 depends on $(cc-option,-fstack-protector-strong) 506 default y 507 help 508 Functions will have the stack-protector canary logic added in any 509 of the following conditions: 510 511 - local variable's address used as part of the right hand side of an 512 assignment or function argument 513 - local variable is an array (or union containing an array), 514 regardless of array type or length 515 - uses register local variables 516 517 This feature requires gcc version 4.9 or above, or a distribution 518 gcc with the feature backported ("-fstack-protector-strong"). 519 520 On an x86 "defconfig" build, this feature adds canary checks to 521 about 20% of all kernel functions, which increases the kernel code 522 size by about 2%. 523 524config ARCH_SUPPORTS_SHADOW_CALL_STACK 525 bool 526 help 527 An architecture should select this if it supports Clang's Shadow 528 Call Stack, has asm/scs.h, and implements runtime support for shadow 529 stack switching. 530 531config SHADOW_CALL_STACK 532 bool "Clang Shadow Call Stack" 533 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 534 help 535 This option enables Clang's Shadow Call Stack, which uses a 536 shadow stack to protect function return addresses from being 537 overwritten by an attacker. More information can be found from 538 Clang's documentation: 539 540 https://clang.llvm.org/docs/ShadowCallStack.html 541 542 Note that security guarantees in the kernel differ from the ones 543 documented for user space. The kernel must store addresses of shadow 544 stacks used by other tasks and interrupt handlers in memory, which 545 means an attacker capable reading and writing arbitrary memory may 546 be able to locate them and hijack control flow by modifying shadow 547 stacks that are not currently in use. 548 549config SHADOW_CALL_STACK_VMAP 550 bool "Use virtually mapped shadow call stacks" 551 depends on SHADOW_CALL_STACK 552 help 553 Use virtually mapped shadow call stacks. Selecting this option 554 provides better stack exhaustion protection, but increases per-thread 555 memory consumption as a full page is allocated for each shadow stack. 556 557config LTO 558 bool 559 560config ARCH_SUPPORTS_LTO_CLANG 561 bool 562 help 563 An architecture should select this option if it supports: 564 - compiling with Clang, 565 - compiling inline assembly with Clang's integrated assembler, 566 - and linking with LLD. 567 568config ARCH_SUPPORTS_THINLTO 569 bool 570 help 571 An architecture should select this if it supports Clang ThinLTO. 572 573config THINLTO 574 bool "Use Clang's ThinLTO (EXPERIMENTAL)" 575 depends on LTO_CLANG && ARCH_SUPPORTS_THINLTO 576 default y 577 help 578 Use ThinLTO to speed up Link Time Optimization. 579 580choice 581 prompt "Link-Time Optimization (LTO) (EXPERIMENTAL)" 582 default LTO_NONE 583 help 584 This option turns on Link-Time Optimization (LTO). 585 586config LTO_NONE 587 bool "None" 588 589config LTO_CLANG 590 bool "Use Clang's Link Time Optimization (LTO) (EXPERIMENTAL)" 591 depends on ARCH_SUPPORTS_LTO_CLANG 592 depends on !KASAN 593 depends on !FTRACE_MCOUNT_RECORD || HAVE_C_RECORDMCOUNT 594 depends on CC_IS_CLANG && CLANG_VERSION >= 100000 && LD_IS_LLD 595 select LTO 596 help 597 This option enables Clang's Link Time Optimization (LTO), which allows 598 the compiler to optimize the kernel globally at link time. If you 599 enable this option, the compiler generates LLVM IR instead of object 600 files, and the actual compilation from IR occurs at the LTO link step, 601 which may take several minutes. 602 603endchoice 604 605config CFI_CLANG 606 bool "Use Clang's Control Flow Integrity (CFI)" 607 depends on LTO_CLANG && KALLSYMS 608 help 609 This option enables Clang's Control Flow Integrity (CFI), which adds 610 runtime checking for indirect function calls. 611 612config CFI_CLANG_SHADOW 613 bool "Use CFI shadow to speed up cross-module checks" 614 default y 615 depends on CFI_CLANG 616 help 617 If you select this option, the kernel builds a fast look-up table of 618 CFI check functions in loaded modules to reduce overhead. 619 620config CFI_PERMISSIVE 621 bool "Use CFI in permissive mode" 622 depends on CFI_CLANG 623 help 624 When selected, Control Flow Integrity (CFI) violations result in a 625 warning instead of a kernel panic. This option is useful for finding 626 CFI violations during development. 627 628config HAVE_ARCH_WITHIN_STACK_FRAMES 629 bool 630 help 631 An architecture should select this if it can walk the kernel stack 632 frames to determine if an object is part of either the arguments 633 or local variables (i.e. that it excludes saved return addresses, 634 and similar) by implementing an inline arch_within_stack_frames(), 635 which is used by CONFIG_HARDENED_USERCOPY. 636 637config HAVE_CONTEXT_TRACKING 638 bool 639 help 640 Provide kernel/user boundaries probes necessary for subsystems 641 that need it, such as userspace RCU extended quiescent state. 642 Syscalls need to be wrapped inside user_exit()-user_enter() through 643 the slow path using TIF_NOHZ flag. Exceptions handlers must be 644 wrapped as well. Irqs are already protected inside 645 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 646 irq exit still need to be protected. 647 648config HAVE_VIRT_CPU_ACCOUNTING 649 bool 650 651config ARCH_HAS_SCALED_CPUTIME 652 bool 653 654config HAVE_VIRT_CPU_ACCOUNTING_GEN 655 bool 656 default y if 64BIT 657 help 658 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 659 Before enabling this option, arch code must be audited 660 to ensure there are no races in concurrent read/write of 661 cputime_t. For example, reading/writing 64-bit cputime_t on 662 some 32-bit arches may require multiple accesses, so proper 663 locking is needed to protect against concurrent accesses. 664 665 666config HAVE_IRQ_TIME_ACCOUNTING 667 bool 668 help 669 Archs need to ensure they use a high enough resolution clock to 670 support irq time accounting and then call enable_sched_clock_irqtime(). 671 672config HAVE_MOVE_PMD 673 bool 674 help 675 Archs that select this are able to move page tables at the PMD level. 676 677config HAVE_ARCH_TRANSPARENT_HUGEPAGE 678 bool 679 680config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 681 bool 682 683config HAVE_ARCH_HUGE_VMAP 684 bool 685 686config ARCH_WANT_HUGE_PMD_SHARE 687 bool 688 689config HAVE_ARCH_SOFT_DIRTY 690 bool 691 692config HAVE_MOD_ARCH_SPECIFIC 693 bool 694 help 695 The arch uses struct mod_arch_specific to store data. Many arches 696 just need a simple module loader without arch specific data - those 697 should not enable this. 698 699config MODULES_USE_ELF_RELA 700 bool 701 help 702 Modules only use ELF RELA relocations. Modules with ELF REL 703 relocations will give an error. 704 705config MODULES_USE_ELF_REL 706 bool 707 help 708 Modules only use ELF REL relocations. Modules with ELF RELA 709 relocations will give an error. 710 711config HAVE_IRQ_EXIT_ON_IRQ_STACK 712 bool 713 help 714 Architecture doesn't only execute the irq handler on the irq stack 715 but also irq_exit(). This way we can process softirqs on this irq 716 stack instead of switching to a new one when we call __do_softirq() 717 in the end of an hardirq. 718 This spares a stack switch and improves cache usage on softirq 719 processing. 720 721config PGTABLE_LEVELS 722 int 723 default 2 724 725config ARCH_HAS_ELF_RANDOMIZE 726 bool 727 help 728 An architecture supports choosing randomized locations for 729 stack, mmap, brk, and ET_DYN. Defined functions: 730 - arch_mmap_rnd() 731 - arch_randomize_brk() 732 733config HAVE_ARCH_MMAP_RND_BITS 734 bool 735 help 736 An arch should select this symbol if it supports setting a variable 737 number of bits for use in establishing the base address for mmap 738 allocations, has MMU enabled and provides values for both: 739 - ARCH_MMAP_RND_BITS_MIN 740 - ARCH_MMAP_RND_BITS_MAX 741 742config HAVE_EXIT_THREAD 743 bool 744 help 745 An architecture implements exit_thread. 746 747config ARCH_MMAP_RND_BITS_MIN 748 int 749 750config ARCH_MMAP_RND_BITS_MAX 751 int 752 753config ARCH_MMAP_RND_BITS_DEFAULT 754 int 755 756config ARCH_MMAP_RND_BITS 757 int "Number of bits to use for ASLR of mmap base address" if EXPERT 758 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 759 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 760 default ARCH_MMAP_RND_BITS_MIN 761 depends on HAVE_ARCH_MMAP_RND_BITS 762 help 763 This value can be used to select the number of bits to use to 764 determine the random offset to the base address of vma regions 765 resulting from mmap allocations. This value will be bounded 766 by the architecture's minimum and maximum supported values. 767 768 This value can be changed after boot using the 769 /proc/sys/vm/mmap_rnd_bits tunable 770 771config HAVE_ARCH_MMAP_RND_COMPAT_BITS 772 bool 773 help 774 An arch should select this symbol if it supports running applications 775 in compatibility mode, supports setting a variable number of bits for 776 use in establishing the base address for mmap allocations, has MMU 777 enabled and provides values for both: 778 - ARCH_MMAP_RND_COMPAT_BITS_MIN 779 - ARCH_MMAP_RND_COMPAT_BITS_MAX 780 781config ARCH_MMAP_RND_COMPAT_BITS_MIN 782 int 783 784config ARCH_MMAP_RND_COMPAT_BITS_MAX 785 int 786 787config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 788 int 789 790config ARCH_MMAP_RND_COMPAT_BITS 791 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 792 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 793 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 794 default ARCH_MMAP_RND_COMPAT_BITS_MIN 795 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 796 help 797 This value can be used to select the number of bits to use to 798 determine the random offset to the base address of vma regions 799 resulting from mmap allocations for compatible applications This 800 value will be bounded by the architecture's minimum and maximum 801 supported values. 802 803 This value can be changed after boot using the 804 /proc/sys/vm/mmap_rnd_compat_bits tunable 805 806config HAVE_ARCH_COMPAT_MMAP_BASES 807 bool 808 help 809 This allows 64bit applications to invoke 32-bit mmap() syscall 810 and vice-versa 32-bit applications to call 64-bit mmap(). 811 Required for applications doing different bitness syscalls. 812 813# This allows to use a set of generic functions to determine mmap base 814# address by giving priority to top-down scheme only if the process 815# is not in legacy mode (compat task, unlimited stack size or 816# sysctl_legacy_va_layout). 817# Architecture that selects this option can provide its own version of: 818# - STACK_RND_MASK 819config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 820 bool 821 depends on MMU 822 select ARCH_HAS_ELF_RANDOMIZE 823 824config HAVE_COPY_THREAD_TLS 825 bool 826 help 827 Architecture provides copy_thread_tls to accept tls argument via 828 normal C parameter passing, rather than extracting the syscall 829 argument from pt_regs. 830 831config HAVE_STACK_VALIDATION 832 bool 833 help 834 Architecture supports the 'objtool check' host tool command, which 835 performs compile-time stack metadata validation. 836 837config HAVE_RELIABLE_STACKTRACE 838 bool 839 help 840 Architecture has a save_stack_trace_tsk_reliable() function which 841 only returns a stack trace if it can guarantee the trace is reliable. 842 843config HAVE_ARCH_HASH 844 bool 845 default n 846 help 847 If this is set, the architecture provides an <asm/hash.h> 848 file which provides platform-specific implementations of some 849 functions in <linux/hash.h> or fs/namei.c. 850 851config HAVE_ARCH_NVRAM_OPS 852 bool 853 854config ISA_BUS_API 855 def_bool ISA 856 857# 858# ABI hall of shame 859# 860config CLONE_BACKWARDS 861 bool 862 help 863 Architecture has tls passed as the 4th argument of clone(2), 864 not the 5th one. 865 866config CLONE_BACKWARDS2 867 bool 868 help 869 Architecture has the first two arguments of clone(2) swapped. 870 871config CLONE_BACKWARDS3 872 bool 873 help 874 Architecture has tls passed as the 3rd argument of clone(2), 875 not the 5th one. 876 877config ODD_RT_SIGACTION 878 bool 879 help 880 Architecture has unusual rt_sigaction(2) arguments 881 882config OLD_SIGSUSPEND 883 bool 884 help 885 Architecture has old sigsuspend(2) syscall, of one-argument variety 886 887config OLD_SIGSUSPEND3 888 bool 889 help 890 Even weirder antique ABI - three-argument sigsuspend(2) 891 892config OLD_SIGACTION 893 bool 894 help 895 Architecture has old sigaction(2) syscall. Nope, not the same 896 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 897 but fairly different variant of sigaction(2), thanks to OSF/1 898 compatibility... 899 900config COMPAT_OLD_SIGACTION 901 bool 902 903config 64BIT_TIME 904 def_bool y 905 help 906 This should be selected by all architectures that need to support 907 new system calls with a 64-bit time_t. This is relevant on all 32-bit 908 architectures, and 64-bit architectures as part of compat syscall 909 handling. 910 911config COMPAT_32BIT_TIME 912 def_bool !64BIT || COMPAT 913 help 914 This enables 32 bit time_t support in addition to 64 bit time_t support. 915 This is relevant on all 32-bit architectures, and 64-bit architectures 916 as part of compat syscall handling. 917 918config ARCH_NO_PREEMPT 919 bool 920 921config ARCH_SUPPORTS_RT 922 bool 923 924config CPU_NO_EFFICIENT_FFS 925 def_bool n 926 927config HAVE_ARCH_VMAP_STACK 928 def_bool n 929 help 930 An arch should select this symbol if it can support kernel stacks 931 in vmalloc space. This means: 932 933 - vmalloc space must be large enough to hold many kernel stacks. 934 This may rule out many 32-bit architectures. 935 936 - Stacks in vmalloc space need to work reliably. For example, if 937 vmap page tables are created on demand, either this mechanism 938 needs to work while the stack points to a virtual address with 939 unpopulated page tables or arch code (switch_to() and switch_mm(), 940 most likely) needs to ensure that the stack's page table entries 941 are populated before running on a possibly unpopulated stack. 942 943 - If the stack overflows into a guard page, something reasonable 944 should happen. The definition of "reasonable" is flexible, but 945 instantly rebooting without logging anything would be unfriendly. 946 947config VMAP_STACK 948 default y 949 bool "Use a virtually-mapped stack" 950 depends on HAVE_ARCH_VMAP_STACK && !KASAN 951 ---help--- 952 Enable this if you want the use virtually-mapped kernel stacks 953 with guard pages. This causes kernel stack overflows to be 954 caught immediately rather than causing difficult-to-diagnose 955 corruption. 956 957 This is presently incompatible with KASAN because KASAN expects 958 the stack to map directly to the KASAN shadow map using a formula 959 that is incorrect if the stack is in vmalloc space. 960 961config ARCH_OPTIONAL_KERNEL_RWX 962 def_bool n 963 964config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 965 def_bool n 966 967config ARCH_HAS_STRICT_KERNEL_RWX 968 def_bool n 969 970config STRICT_KERNEL_RWX 971 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 972 depends on ARCH_HAS_STRICT_KERNEL_RWX 973 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 974 help 975 If this is set, kernel text and rodata memory will be made read-only, 976 and non-text memory will be made non-executable. This provides 977 protection against certain security exploits (e.g. executing the heap 978 or modifying text) 979 980 These features are considered standard security practice these days. 981 You should say Y here in almost all cases. 982 983config ARCH_HAS_STRICT_MODULE_RWX 984 def_bool n 985 986config STRICT_MODULE_RWX 987 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 988 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 989 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 990 help 991 If this is set, module text and rodata memory will be made read-only, 992 and non-text memory will be made non-executable. This provides 993 protection against certain security exploits (e.g. writing to text) 994 995# select if the architecture provides an asm/dma-direct.h header 996config ARCH_HAS_PHYS_TO_DMA 997 bool 998 999config ARCH_HAS_REFCOUNT 1000 bool 1001 help 1002 An architecture selects this when it has implemented refcount_t 1003 using open coded assembly primitives that provide an optimized 1004 refcount_t implementation, possibly at the expense of some full 1005 refcount state checks of CONFIG_REFCOUNT_FULL=y. 1006 1007 The refcount overflow check behavior, however, must be retained. 1008 Catching overflows is the primary security concern for protecting 1009 against bugs in reference counts. 1010 1011config REFCOUNT_FULL 1012 bool "Perform full reference count validation at the expense of speed" 1013 help 1014 Enabling this switches the refcounting infrastructure from a fast 1015 unchecked atomic_t implementation to a fully state checked 1016 implementation, which can be (slightly) slower but provides protections 1017 against various use-after-free conditions that can be used in 1018 security flaw exploits. 1019 1020config HAVE_ARCH_COMPILER_H 1021 bool 1022 help 1023 An architecture can select this if it provides an 1024 asm/compiler.h header that should be included after 1025 linux/compiler-*.h in order to override macro definitions that those 1026 headers generally provide. 1027 1028config HAVE_ARCH_PREL32_RELOCATIONS 1029 bool 1030 help 1031 May be selected by an architecture if it supports place-relative 1032 32-bit relocations, both in the toolchain and in the module loader, 1033 in which case relative references can be used in special sections 1034 for PCI fixup, initcalls etc which are only half the size on 64 bit 1035 architectures, and don't require runtime relocation on relocatable 1036 kernels. 1037 1038config ARCH_USE_MEMREMAP_PROT 1039 bool 1040 1041config LOCK_EVENT_COUNTS 1042 bool "Locking event counts collection" 1043 depends on DEBUG_FS 1044 ---help--- 1045 Enable light-weight counting of various locking related events 1046 in the system with minimal performance impact. This reduces 1047 the chance of application behavior change because of timing 1048 differences. The counts are reported via debugfs. 1049 1050# Select if the architecture has support for applying RELR relocations. 1051config ARCH_HAS_RELR 1052 bool 1053 1054config RELR 1055 bool "Use RELR relocation packing" 1056 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1057 default y 1058 help 1059 Store the kernel's dynamic relocations in the RELR relocation packing 1060 format. Requires a compatible linker (LLD supports this feature), as 1061 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1062 are compatible). 1063 1064config ARCH_HAS_MEM_ENCRYPT 1065 bool 1066 1067source "kernel/gcov/Kconfig" 1068 1069source "scripts/gcc-plugins/Kconfig" 1070 1071endmenu 1072